This study was conducted to examine sexual dimorphic effects of highly palatable food access during adolescence and youth on psychoemotional behaviors of rats and its underlying neural mechanism.

Male and female Sprague Dawley pups had free access to chocolate cookie rich in fat (highly palatable food) from postnatal day 28 in addition to ad libitum chow, and the control groups received chow only. The food conditions were continued though out the entire experimental period, and the neurochemical and behavioral measurements were performed during young adulthood. Corticosterone levels during 2h of restraint stress were analyzed with radioimmunoassay, and ΔFosB and brain-derived neurotrophic factor (BDNF) expression in the nucleus accumbens (NAc) with western blot analysis.

Cookie access did not affect body weight gain and total caloric intake in both sexes; however, it increased retroperitoneal fat depot only in males. The time spent in open arms during elevated plus maze test was decreased and immobility during forced swim test was increased in cookie-fed males, but not in cookie-fed females. Main effect of food condition on the stress-induced corticosterone increase was observed in males, but not in females, and cookie access increased BDNF expression in the NAc only in males.

Increased BDNF expression in the NAc and fat depot, in addition to the HPA axis dysfunction, may play roles in the pathophysiology of depression- and/or anxiety-like behaviors induced by cookie access.